Hi,

On 13-Oct-25 10:04 AM, Javier Martinez Canillas wrote:
> Thomas Zimmermann <[email protected]> writes:
> 
> Hello Hans,
> 
>> Hi Hans
>>
>> Am 11.10.25 um 12:02 schrieb Hans de Goede:
>>> Hi,
>>>
>>> A while ago I did a blogpost about not having the native GPU drivers in
>>> the initrd: https://hansdegoede.dreamwidth.org/28291.html
>>>
>>> With the Fedora /boot partition size increase there has been renewed
>>> interest in this and as a result I got an interesting comment on
>>> the blog post pointing out that there are EFI protocols to get EDID
>>> info for the monitor (presumably for the one the GOP has lit up).
>>>
>>> It would be useful to see if we can hook this up so that the simpledrm
>>> device can report the physical dimensions of the screen and the boot
>>> splash does not need to guess the DPI and thus does not need to guess
>>> whether to do hiDPI scaling or not. The comment is here:
>>>
>>> https://hansdegoede.dreamwidth.org/28291.html?thread=14467#cmt14467
>>>
>>> and it points to:
>>>
>>> https://uefi.org/sites/default/files/resources/2_-_AMD_UEFI_Plugfest_EDID_Spring2012.pdf
>>> https://uefi.org/specs/UEFI/2.9_A/12_Protocols_Console_Support.html
>>>
>>> Unfortunately I do not have time to work on this myself, hence this
>>> email in the hope that someone else can pick this idea up.
>>
>> There are now efidrm and vesadrm, which support specifically the 
>> features that we get from the rsp. standards, hardware  and bootloader. 
>> For VESA and EFI the EDID can be transferred from grub via bootparams. A 
>> patch [1] is on its way into upstream grub. The Linux kernel stores that 
>> data in edid_info, from where it is picked up by efidrm and vesadrm.  If 
>> the EFI framebuffer comes directly from the EFI calls, we need to 
>> implement this in the kernel, but the principle is the same. I also have 
>> ideas for making this work on Coreboot.
>>
>> For simpledrm, I'd rather strip if from the ability to use EFI/VESA 
>> framebuffers and focus on simple-framebuffer DT nodes. These sometimes 
>> come with DPI information. Maybe we could extend the DT to support EDID 
>> as well.
>>
>> [1] https://lists.gnu.org/archive/html/grub-devel/2025-10/msg00043.html
>>
>> I have long been working on all this and it is now slowly coming together.
>>
> 
> I agree with Thomas.
> 
> We are still not enabling these DRM drivers in Fedora though, but maybe it
> is time to do that and just disable CONFIG_SYSFB_SIMPLEFB. I can propose a
> change request for Fedora 44 to do this.

Trying to drive this forward by enabling this in Fedora 44 so this gets
more test coverage sounds like a good plan to me!

Thanks & Regards,

Hans


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